This invention relates to a method and an apparatus for controlling terminals on a communication network, especially, a terminal control method featuring a unique address system used for transmission and reception of messages to and from terminals on a communication network.
FIG. 1 is a schematic diagram illustrating a communication network to which a transmission system of the invention is applied;
FIG. 2 illustrates a prior art address system for various devices;
FIGS. 3A, 3B and 3C illustrate examples in which the prior art address system is applied to various devices shown in FIG. 1;
FIG. 4 shows allotment in a function address table based on the prior art address system;
FIG. 5 illustrates a format of a prior art control message on a home bus system control channel;
FIG. 6 illustrates an example of the sequence for controlling the devices having the address formats shown in FIG. 3;
FIGS. 7A and 7B illustrate examples of the message format used in the sequence shown in FIG. 6;
FIG. 8 is a schematic diagram illustrating a prior art received message processor for a TV;
FIG. 9 is a schematic diagram illustrating a prior art received message processor of telephone;
FIG. 10 is a schematic diagram illustrating a prior art received message processor of TV with telephone;
FIG. 11 is a schematic diagram illustrating a prior art controller; and
FIGS. 12A and 12B illustrate examples of address management table for devices to be managed which are used in the prior art controller.
The prior art will now be described referring to FIGS. 1 to 12. As shown in FIG. 1, a plurality of terminals 11 to 14 are connected to a transmission line 10 to communicate mutually in a communication network, and each terminal comprises a single device or a composite device consisting of a plurality of devices. Conventionally, an address system necessary for transmission and reception of messages to and from the terminals is designed, as shown in FIG. 2, to include a device address (DA) 21 assigned to individual terminals and function addresses (FA's) 22 respectively assigned to functions of each terminal. A value of the FA represents predetermined contents and a table as shown in FIG. 4 is constructed. According to the table of FIG. 4, a FA for timer 41, for example, has specific values &lt;FAxy&gt;. Thus, the timer FA 41 has four values &lt;FA00&gt; to &lt;FA03&gt; and these values are effective to identify a plurality of timers possessed by a terminal comprising a composite device to be described later. According to this address system, the TV11, telephone 12 and TV with telephone 13 have address formats as shown in FIG. 3. More particularly, the TV 11 has a TV 31 as a DA and a FA having specific values of a timer 32a (&lt;FA00&gt;), a monitor 32b (&lt;FA30&gt;) and a tuner 32C (&lt;FA20&gt;). The telephone 12 has a telephone 33 as a DA and a FA having specific values of a timer 34a (&lt;FA00&gt;), a display 34b (&lt;FA40&gt;) and a telephone set 34C (&lt;FA50&gt;).
The TV with telephone 13 standing for a composite device having integral VTR, telephone set and TV has a TV with telephone 35 as a DA and a FA having specific values of a timer for VTR or timer 1 36a (&lt;FA00&gt;), a deck for VTR 36b (&lt;FA10&gt;), a tuner for VTR or tuner 1 36c ((FA20&gt;), a timer for TV or timer 2 36d (&lt;FA01&gt;), a monitor for TV 36e (&lt;FA30&gt;), a tuner for TV or tuner 2 36f (&lt;FA21&gt;), a timer for telephone or timer 3 36g (&lt;FA20&gt;), a display for telephone 36h (&lt;FA40&gt;) and a telephone set for telephone 36i (&lt;FA50&gt;). There exist in the TV with telephone 13 three timers (timer 1 36a, timer 2 36d and timer 3 36g) and two tuners (tuner 1 36c and tuner 2 36f) as viewed from outside but information concerning which device the FA is destined for is not added. Therefore, the controller 14 for controlling the terminals connected to the system has to be stored precedently with data for the controllable terminals upon establishment of the system. Conventionally, the controller 14 is constructed as exemplified in FIG. 11. The controller 14 comprises a transmission/reception control processor 111 responsive to a request for control to perform transmission/reception control of a message in accordance with the communication scheme on the transmission line, a received message control processor 113 which performs analysis of a FA and the like of a received message to decide whether the received message is a message to be processed, a control input unit 115 for inputting a request for system control and the like, a display unit 116 for displaying outputs such as control results, a system control processing unit 114 adapted to control the controller 14 and manage and control the system, a connectable terminal address information holding unit 117 operable to control and manage the system, and a transmission message control processing unit 112 responsive to information from the system control processing unit 114 to control transmission of message.
As an example, consider a case where the controller 14 changes, pursuant to sequence as shown in FIG. 6, setting of timer in order to effect time correction for TV in the system which is a home bus system using a control message as shown in FIG. 5 for controlling terminals. It will be appreciated from FIGS. 1 and 3 that two terminals, TV 11 and TV with telephone 13, have a timer for TV. Upon start-up of the system, it is necessary for the connectable terminal address information holding unit 117 of controller 14 to hold in advance the following information:
(I) Information about the value of DA 31 of the TV 11 and the value (&lt;FA00&gt;) of the timer FA 32a.
(II) Information about the value of DA 35 of the TV with telephone 13 and the value (&lt;FA01&gt;) of the timer 2 FA 36d. In the controller 14, the connectable terminal address information holding unit 114 holds the above information as a table shown at (12B) in FIG. 12. Referring to FIG. 5, the message on a home bus control channel as shown in FIG. 6 has a format including a priority code PR 51 for determining priority of communications on the transmission line, a field SA 52 indicative of an address of an originator, a field DA 53 indicative of an address of a destination, a field CC 54 of a message control code indicative of the kind of information in a DATA field 56 containing the contents of the message, a DATA field length code BC 55 indicative of the size of the DATA field 56, and a frame check code FCC 57 used to effect frame check of the message by utilizing two's complement of the sum of the bits ranging from SA 52 to the final byte of DATA 56. To detail the DATA field 56, it has a sub-bus originator address SA' 56b indicative of an originator address in the event that a message is issued from a terminal connected to a different transmission line, a destination address DA' 56c indicative of a destination address in the event that a message is destined for a terminal connected to a different transmission online, an originator function address SFA 56d indicative of an originator (FA) in the originator terminal, a destination function address DFA 56e indicative of a destination (FA) in the destination terminal, an operation code OPC 56f for designating a command for control, an operand code OPR 56g for designating details of the contents of the control command, a termination code TC 56h, and a header HD 56a having information for designating the presence or absence of the SFA 56d, DFA 56e, DA' 56c and SA' 56b and a table (service group) of the command designated by the OPC 56f.
In the controller 14, when a request for the simultaneous change of timers for TV in the system is input from the control input unit 115, the system processing unit 114 determines the inputted request, builds up a transmission message A as shown at (7-1) in FIG. 7 destined for the TV 11 on the basis of a management table as shown at (12-2) in FIG. 12 stored in the connectable terminal address information holding unit 117, and transfers the message A to the transmission message control processing unit 112. At that time, in the message A, a field DA 53 indicates a code 71 indicative of a DA of the TV 11 and a field DFA 56e indicates a code 72, &lt;FA00&gt;, indicative of a FA of the timer 32a. The transmission message control processing unit 112 then performs a transmission processing of the message A sent from the system control processing unit 114 and transmits the message to the TV 11 through the transmission/reception control processor 111, as indicated at 61 in FIG. 6.
In the TV 11 constructed as shown in FIG. 8, a transmission/reception control processor 81 receives the message A and a DFA decision processing unit 83 of a received message control processor 82 decides the field DFA. Since the DFA in this message A indicates the timer code 72 &lt;FA00&gt;, the DFA decision processing unit 83 actuates a timer &lt;FA00&gt; destined message control processing unit 85 to carry out a processing of change of timer. Subsequently, the controller 14 builds up a message B as shown at (7-2) in FIG. 7, as in the case of the message A, and transmits the message B to the TV with telephone 13, as indicated at 62 in FIG. 6. At that time, DA 53 of the message B indicates a code 73 indicative of a DA of the TV with telephone 13 and DFA 56e indicates a code 74&lt;FA01&gt;indicative of a FA of the TV timer 36d. In the TV with telephone 13 constructed as shown in FIG. 10, a transmission/reception control processor 101 receives the message B and a DFA decision processing unit 103 of a received message control processor 102 determines the DFA. Since the DFA in this message B indicates the timer 2 code 74 &lt;FA01&gt;, the DFA decision processing unit 103 actuates a timer &lt;FA01&gt; destined message control processing unit 107 to carry out a processing of change of TV timer. In the prior art, the value of the message destined address DA 53 and the value of the code DFA 56e in the message A shown at (7-1) in FIG. 7 and the message B shown at (7-2) in FIG. 7 are different for terminals and therefore the TV 11 and TV with telephone 13 cannot be controlled simultaneously. This leads to such potential danger that transmission/reception of a plurality of messages occur between the messages A and B and concurrence of the messages A and B is lost. This disadvantage is especially serious when a plurality of terminals are desired to be controlled simultaneously in order to effect, for example, the time correction of timers. Further, in comparison with the received message control processor 82 of the TV 11 constructed as shown in FIG. 8 and a received message control processor 92 of the telephone 12 constructed as shown in FIG. 9 by comparing components 93 to 97 corresponding to components 83 to 87 of the TV 11, the received message control processor 102 of the TV with telephone 13 having additional function of VTR is differently constructed and has values of FA, different from those of the processing units of the TV 11 and telephone 12, in order to handle plural timers, destined for different locations i.e., timer 1 36a, timer 2 36d and timer 3 36g shown in FIG. 3, so that alternation is required to permit the processor 102 to take the part of the processor 82 and 92.
As described above, the prior art has the following disadvantages:
(i) Even when it is preferable to control simultaneously functions which are the same for a plurality of terminals, different addresses are sometimes assigned to the same function in the individual terminals and consequently simultaneous control of transmission of control messages cannot be achieved using a multi-address message destined for the individual terminals. As a result, separate control data must be transmitted to each terminal, thus making the control processing in the communication system complicated and the number of devices to be controlled is increased to increase traffic.
(ii) In order to control a function of a terminal in the system, a control terminal (controller) has to hold, according to precedence, data of the internal construction of the controlled terminal. Accordingly, when a new terminal is connected to the system or an existing terminal is connected to the system or an existing terminal is removed, information registered in the controller must always be updated, in particular, information concerning the newly connected terminal must be registered and this degrades extensibility of the system.
(iii) When developing composite devices, the control processing units of devices constituting the existing terminal can not be utilized without alternation. This impairs the versatility of the control processing unit of the terminal.